Implantable cardioverter-defibrillators (ICDs) have been developed that employ detection algorithms capable of recognizing and treating atrial tachycardias and atrial fibrillation. In general, ICDs are designed to treat such tachycardias with antitachycardia pacing and low-energy cardioversion shocks in conjunction with back-up defibrillation therapy. These ICDs monitor the heart rate and the onset of the arrhythmia by sensing endocardial signals and determining when the heart is in need of either cardioversion to treat a given tachycardia or of defibrillation to treat a fibrillation condition.
Certain ICDs have been designed with dual chamber sensing capabilities to detect and analyze both ventricular and atrial endocardial signals. This increase in cardiac signal input to the ICD has provided an opportunity to determine the origin and the nature of atrial and ventricular tachyarrhythmia, and to reduce the frequency of inappropriate therapy being delivered to an implant patient.
However, while the combination of antitachycardia pacing with low and high energy shock delivery, as well as backup bradycardia pacing, in ICDs has expanded the number of clinical situations in which the devices may appropriately be employed, improved means of coordinating atrial rate information in a way that results in a system that effectively and efficiently treats atrial tachyarrhythmias is still desired.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading the present specification, there is a need in the art for improved atrial arrhythmia detection and therapy techniques. There exists a further need for such techniques that provide for enhanced detection and treatment of atrial arrhythmias under conditions of varying cardiac activity, such as occurs during exercise. The present invention fulfills these and other needs.